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Redbeardroe t1_j5lsnu8 wrote

So is the ELI5 on this essentially the earths core stopped rotating and is about to reverse?

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shiruken OP t1_j5lu9td wrote

Not quite, it's just slowing down relative to the rest of the planet. Previously it was moving slightly faster than the rest of the planet.

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justahomeboy t1_j5lxhib wrote

Do you mind explaining how the core and the rest of the planet can have different rotation speeds? I haven’t taken science courses since college so I’m ignorant to the subject matter.

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shiruken OP t1_j5m0uqb wrote

Don't really know the specifics, but it has to do with the structure of the Earth where the outer core is liquid while the inner core is solid. Anytime you start spinning layers with liquid, things get complicated.

The New York Time's coverage of this research offers this explanation:

>What’s going on? One idea is that two titanic forces are battling for control over the world’s heart. Earth’s magnetic field, generated by swirling iron currents in the liquid outer core, is pulling at the inner core, causing it to spin. That impulse is countered by the mantle, the mucilaginous layer above the outer core and below Earth’s crust, the immense gravitational field of which grasps the inner core and slows its spin.

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Bofgrey t1_j5nuek4 wrote

It is simple to understand if you grab an uncooked egg, spin it around on a table, bring it to a sudden stop by putting your hand on top, and then quickly lift your hand again. The rotating insides of the egg will bring it in motion again. (This is also a trick to check if an egg is cooked or not)

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KubaKuba t1_j5m0sp9 wrote

I wonder if orbit is a potential cause?

I could imagine rotational artifacts from a non perfectly circular orbital path causing a rotational speed difference between the core and the shell of the earth.

As a matter of fact I would be surprised if it wasn't that.

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Rhaski t1_j5njwbu wrote

No. It's resonance. As it spins, it increases and decreases speed in a periodic fashion. This frequency is a harmonic just like when you flick a wine glass and it rings for a while, but instead of being an inward/outward flexing motion, it's an angular oscillation. This happens in the rotating assembly of some engine configurations too (such as V6 engines), so they have to have a harmonic balancer to smooth out this angular oscillation or it makes everything vibrate horrible when the RPMs match the harmonic frequency of the crankshaft and it can break. It's also observed in shaft couplings like U-joints. This is why the Constant Velocity (CV) shaft was invented, because traditional U-joints operating on an angle (such as in driving a front wheel whilst turning) caused fierce angular vibration to travel down the driveshaft and at the right frequency, it could resonate and lead to failure of the driveshaft or other components. We are seeing this on a much larger system and, consequently, we see a much lower harmonic frequency. In the order of cycles per century rather than cycles per second

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jpipersson t1_j5n9r4m wrote

>So is the ELI5 on this essentially the earths core stopped rotating and is about to reverse?

No. This is not what it says. Reread more carefully. Perhaps also read something about the conservation of angular momentum.

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